Hydrodesulfurization and blending of residue-containing petroleum oil

ABSTRACT

Petroleum oils of reduced sulfur content are produced by introducing into a catalytic hydrodesulfurization zone a residuecontaining petroleum oil of which at least 10 volume per cent boils below 1,000*F. separating the hydrodesulfurization zone effluent into a fraction boiling below about 1,000*F. and a fraction boiling above about 1,000*F. desulfurizing the fraction boiling below about 1,000*F. and combining the product with the fraction boiling above about 1,000*F. The catalyst in the first hydrodesulfurization should have a surface area of at least 250 m2/g., a pore volume of at least 0.6 cc/g and should contain at least 2 percent by weight silica.

, United States Patent Nelson et al.

[54] HYDRODESULFURIZATION AND 3,362,901 1/1968 Szepe et a1 ..208/2l0 BLENDIN RESIDUECONTAINING 3,509,044 4/1970 Adams et al ..208/216 PETROLEUM OIL 3,617,525 1 1/1971 Moritz et al. ..208/212 [72] Inventors: Gerald VQNelson, Nederland; Wilprimary E i 1b n E G m liam R. Coons, Jr., Port Arthur, Assistant Examiner-G. J. Crasanakis both of Tex.; Glenn C. Wray, Dyer- Attorney-K. E. Kavanagh, Thomas H. Whaley and sburg, Tenn. Robert Knox, Jr.

[73] Asslgnee: Texaco Inc., New York, N.Y. 57] ABSTRACT [22] Flled: March 1971 Petroleum oils of reduced sulfur content are produced [21] Appl. No.: 123,004 by introducing into a catalytic hydrodesulfurization zone a residue-containing petroleum oil of which at Related US. Application Data least 10 volume per cent boils below 1,000F. separating the hydrodesulfurization zone efi'luent into a frac- .[63] 33 g"? 787908 tion boiling below about 1,000F. and a fraction boila an ing above about 1,000F. desulfurizing the fraction r boiling below about 1,000F. and combining the [52] US. Cl ..208/2l0 I product with the fraction boiling above about IOOOQF Ill. Cl. Th t l t i the first hydrodesulfurization should Fleld of Search 58, 59, l, have a surface area of at least In /g a pore 208/2 213 volume of at least 06 cc/g and should contain' at least 2 percent by weight silica. [56] References Cited 6 Claims, 2 Drawing Figures UNITED STATES PATENTS 3,179,586 4/ 1965 Honerkamp ..208/210 90 I Q6 r 52 /3 Z2" Z3 L /3 72 //6 24 75 5, 3 2/ 25 Desu/furlkafin /9 I @Eackr/ 20 l epora/br kill $2321 2: I 76 4 F/vcfianafir yefiafafdf JgAara/ar 12 PATENTEDSEP 12 I972 SHEEI 2 BF 2 HYDRODESULFURIZATION AND BLENDING OF RESIDUE-CONTAINING PETROLEUM OIL This application is a continuation of Ser. No. 787,908, filedDec. 30, 1968, now abandoned.

This invention is concerned with the removal of sulfur from petroleum hydrocarbon liquids. More particularly it is concerned with the production of heavy hydrocarbon fuels of low sulfur content.

The hydrodesulfurization of light petroleum hydrocarbon liquids is well known and has been practiced for many years. Generally, sulfur is present in petroleum in the form of mercaptans, sulfides, di-sultides and in complex compounds containing ring structures such as thiophenes. Inthe catalytic desulfurization of lighter petroleum fractions such as gasoline, naphtha and kerosine the sulfur is present to a large extent in the form of easily removable mercaptans requiringless severe desulfurization; conditions which make for longcatalystlife. The catalyst life is also prolonged in the desulfurization of such light fractions by the low content of polynuclear aromatics present in the charge.

Up until recently no serious attempts have been made to desulfurize heavy residual type petroleum fractions, since these materials have ordinarily been burned as industrial fuels. However, with the recent interest in the prevention of air pollution it has become necessary to resort to the use of industrial fuels of low sulfur content.

The catalytic desulfurization of residual fuels is much more difiicult than the desulfurization of lighter fractions. When hydrodesulfurizing residual stocks, contaminants such as metals and carbon residue are removed from the residual stock and are deposited on the catalyst. In addition, polynuclear condensed ring aromatic compounds tend to collect on the catalyst and to decompose" with the formation of a coke deposit. These deposits cause deactivation of the catalyst and in processes where the product has a maximum sulfur specification this loss in activity is compensated for by increasing the reaction temperature. Unfortunately,

- when the reaction temperature is increased there is an accompanying increase in'the rate of metals deposition and in the rate of deposition of other contaminants on the catalyst and correspondingly the de-activation rate of the catalyst becomes progressively greater. When the reactor temperature has been increased to the maximum limit of the reactor design or when the amount of the conversion to light materials reaches an undesirable level the unit must be shut down to regenerate or replace the catalyst.

We have discovered a novel process for the desulfurization of residue containing fuel oils. According to our invention there is provided a process for the desulfurization of hydrocarbon oils containing at least 1 percent Conradson Carbon and of which at least 10 volume per cent boils below about 1,000F. which comprises passing said hydrocarbon oil in the presence of hydrogen under desulfurization conditions into contact with a desulfurization catalyst, separating the effluent into a light fraction boiling below about l,0OF. and a heavy fraction boiling above about 1,000F'., cont'acting said light fraction with a desulfurization catalyst under desulfurization conditions and combining the desulfurized light fraction with said heavy fraction.

One of the features of our process is that as the catalyst used for the desulfurization of residual fuels becomes de-activated due to the deposition of metals thereon, its rate of de-activation for the desulfurization of the heavy components is not as rapid as its rate of deactivation for the desulfurization of the lighter components. Another feature is that the rate of de-activa tion of the catalyst for the desulfurization of the heavy portion of the charge is not as rapid when the lighter portion is included in the charge to the desulfurization reaction zone as it is when the heavy portion ischarged alone to the desulfurization reaction zone. In fact, we have found that after prolonged operation the lighter portion of the desulfurized product can have a greater sulfur content than the same fraction of the charge stock. Thus, with the use of a partially deactivated catalyst the sulfur present in the higher boiling compounds is selectively removed. By removing'the lower boiling compounds and hydrodesulfurizing them in a second reactor containing a catalyst that is not being subjected to a high level of contamination and then recombining them with the higher boiling compounds, the overall sulfur reduction is substantially increased.

This permits continued use of the contaminated catalyst for a period far beyond the expected life of the catalyst.

For a better understanding of the process of our invention, reference is'made to the accompanying FIG. I which shows diagrammatically a flow scheme for the practice of one embodiment of our invention. For the sake of simplicity, various items such as valves, pumps, compressors and the like have been omitted.

Referring now to FIG. 1, the charge is introduced into the system through line 11 and with hydrogen from line 12 is introduced into desulfurization reactor 13. Effluent from reactor 13 is transferred through line 14 to high pressure separator 15 from which hydrogen is v removed through line 16 and the separated liquid is passed through line 17 to low pressure separator 18. Gas is removed and sent to gas recovery through line 19 and the bottoms passed through line 20 to fractionator 21. Additional gas is removed through line 22, naphtha is removed through line 23 andthe balance of the liquid product boiling up to about 1,0()0F. is transferred to second desulfurization reactor 24 through line 25. With hydrogen from line 26 the reactant stream from line 25 is subjected to hydrodesulfurization conditions and the efl'luent removed from reactor 24 and in troduced into high pressure separator 30 through line 29. Recycle hydrogen is removed and recycled to reactor 13 through line 12. The liquid portion of the effluent from high pressure separator 30 is transferred to low pressure separator 33 through line 32. Gas is withdrawn through line 40 and sent to gas recovery. The liquid effluent from low pressure separator 33 is sent to fractionator 46 through line 35 from which it is separated into a light fraction withdrawn through line 50, an intermediate fraction withdrawn through line 52 and a heavy fraction withdrawn through line 55. The heavy fraction is combined with that fraction having an initial boiling point of about 1,000F. in line 54. Makeup hydrogen may be introduced into the system through line 57. A portion of the hydrogen recovered from high pressure separator 15 may be recycled to reactor 13 by means of line 60. Advantageously, to maintain temperature control, a portion of the hydrogen from line 60 may be introduced into reactor 13 through lines 71 and 72. Similarly, temperature control may be obtained in reactor 24 by the introduction of hydrogen through lines 75 and 76.

The process of our invention is applicable to a wide variety of charge stocks including whole crude, atmospheric residuum, vacuum residuum, shale oils, tar sand oils, residual fuel oil blends and the like. The charge to the catalytic reaction zone should contain at least 1 percent Conradson Carbon and should also contain at least volume percent boiling below about 1,000F. Advantageously, a portion of light material produced as a by-product of our process may be recycled to supply at least a portion of the lighter material to be included as part of the charge. Typically, the charge stocks contain tar and metals, both of which ordinarily have a detrimental effect on the catalyst life and activity.

The reaction conditions may be varied, depending on the amount of desulfurization desired and on the charge stock. In the first reactor the catalyst bed temperature may range from about 600-900F., a preferred range being from 650850F. The hydrogen partial pressure should be within the range of from about 5003,000 psig, a preferred range being from l,0002,000 psig. Hydrogen may be introduced into reactor 13 at a rate of from l000-20,000 scfb, a preferred rate being 3,000l0,000 scfb. Although space velocities of from 0.3-1.5 volumes of oil/volume of catalyst/hr. are preferred, space velocities of from 01-100 may be used. In the second catalytic reaction zone (reactor 24) temperatures may range from 450-900F., hydrogen partial pressures from 300-3,000 psig, hydrogen rates from SOD-20,000 scfb and space velocities from 0. l-20.0. Preferred reaction conditions are temperatures of 500 -800F., hydrogen partial pressures of 500l,500 psig, hydrogen rates of from LOGO-5,000 scfb and space velocities of from 0.5-l0.

Hydrogen from any suitable source such as electrolytic hydrogen, hydrogen obtained from the partial combustion of a hydrocarbonaceous material followed by shift conversion and purification or catalytic reformer by-product hydrogen and the like may be used. The hydrogen should have a purity of at least 50 volume percent, satisfactory results having been obtained using hydrogen having a purity of between 75 and 90 volume percent.

The catalysts used in the process of our invention comprise a Group 8 metal compound such as the oxide or sulfide of cobalt,iron or nickel or mixtures thereof advantageously used in conjunction with a Group 6 metal compound such as the oxide or sulfide of molybdenum or tungsten. Ordinarily, the catalyst is charged to the reactor in oxide form although it can be expected that some reduction and some sulfidation takes place during the course of the process so that after being on stream for some time the catalyst is probably a mixture of the metal, the metal sulfide and perhaps the oxide. The Group 8 metal compound may be present in an amount varying from 1 to percent by weight of the catalyst composite. The Group 6 metal compound may be present in an amount ranging from about 5 to 40 percent of the total catalyst composite. Ordinarily, the hydrogenating components are supported on a refractory inorganic oxide such as alumina, zirconia, silica or magnesia or mixtures thereof. Particularly suitable catalysts comprise nickel and tungsten, cobalt and molybdenum or nickel and molybdenum on a refractory support. To obtain particularly long life, the catalyst used in the first reaction zone, to which the residue containing charge is introduced, has a surface area of at least 250 sq. meters per gram, preferably at least 300 sq. meters per gram and a pore volume of at least 0.6 cc per gram. The catalyst for the first reaction zone should also contain at least 2 percent by weight silica.

Although in the drawing reactant flow through the catalytic zone has been depicted as downflow through a fixed bed, it is possible to pass the reactants upwardly or counter-currently through the catalyst bed. It should also be realized that the catalyst may be used in the form of a slurry or as a fluidized bed.

The following examples are presented for illustrative purposes only.

EXAMPLE I In this example, the catalyst has the following composition and characteristics:

TABLE 1 Surface area, mlgm 312 Pore volume, cc/gm 0.66 Bulk density, lbs/ft 44.0 Composition, wt.%:

Co 2.1 Mo 11.0 SiO, 2-4 AI,O remainder Present in oxide form.

TABLE 2 Catalyst Bed temp. F.

Hydrogen partial pressure, psig 1500 Reactor Reed Gas RAte, SCFB 5000 Feed Gas Purity, vol. H,

Space Velocity, v/v/hr. 0.5

Hours on stream 134 1630 5948' Wt. %Ni and V deposited 1.5 9.5 20

Sulfur, wt.

Total Product 0.35 1.13 1.18 IBP 1000F. 0.67 1.99 1.75

Wt. of original catalyst loading.

"Catalyst regenerated at 49241hours using air nitrogen mixture at. 850F. 1

EXAMPLE [I I In this example which is a continuation of Example I, the charge and reactor 1 catalystare the same as in Example I. The catalyst in reactor 2 is a conventional desulfurization catalyst containing 2.6 weight percentcobalt and l0.0weight percent molybdenum supported on alumina. Here, the effluent from reactor 1 is fraction'ated, .the [BP-l ,000F. fraction is separately desulfurized reactor land the liquid product combined with the 1,000F. +fraction of reactor 1 effluent.

Reaction conditions and other data .are tabulated below in Table 3.

table 3 reactor 1 reactor 2 Catalyst bed temperature, F. 775 715 Hydrogen partial pressure, psig 1500 750 Reactor Feed Gas Rate, SCFB S000 2000 Feed Gas Purity, vol.% h: 85 80 Space Velocity, v/v/hr. 0.5 2.0 Time on stream, hours 134 1630 5948 Sulfur content, wt.

Reactor 2 effluent 0.05 0.15 0.19

Total Product 0.20 0.71 0.62

The above data show that the aged catalyst selectively desulfurizes the heavy portionof the charge and that the deactivation rate for the desulfurization of the lighter material is greater than the deactivation rate for the heavier material.

EXAMPLE III This example shows that in the presence of lighter material the deactivation rate of the catalyst for the desulfurization of the 1000F.+ material is lower than when the lighter material is not present. In Run 1, the charge is Atmospheric Reduced Arabian Crude and in Run 2, Arabian Vacuum Residuum. The same catalyst is used as in Example I and reaction conditions are maintained substantially constant, only the tempera ture being varied to maintain a 1.6 percent sulfur con tent in the 1,000F.+ fraction of the product.

Reaction conditions and other data are tabulated below.

TABLE 4 Run 1 Run 2 Charge Gravity, API 15.4 10.4 Sulfur, wt. 3.1 3.7 Conradson Carbon Residue, wt. 10.9 23.4

Metals, ppm

Ni 1 l 24 V 30 64 Distillation, vol.

Operating Conditions I-lydrogen partial pressure, psig 1500 1500 Feed gas rate, SCFB 5000 5000 Hydrogen putity, l l

Space velocity, v/v/hr. 0.5 0.5 Start of run temperature "F. 740 740 Temperature after 64 days, F. 752 800 Sulfur in l000F.+fraction, wt. 1.6 1.59

On the basis of Run 2, the predicted temperature after 64 days on stream for Run 1 should be 767F. since the charge to Run 1 contains only 45 volume percent material boiling above 1,000F. The temperature of 752F. shows that the deactivation rate of the catalyst in Run 1 is less than half of what would be expected It thus appears from the foregoing examples that with a partially deactivated catalyst the desulfurization of the 1,000F.+ fraction seems to be better-when gas oil is present although desulfurization of the'gas oil seems tobe hindered by the presence of the 1,000F.+ fraction. 1

Obviously, various modifications of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore, only suchlimitations should be imposed as are indicated in the appended claims.

WE CLAIM:

1. A process for the production of a residue-containing petroleum oil of reduced sulfur content which comprises contacting in afirst catalytic desulfurization zone at a temperature between about 600 and 900F., a pressure between about 500 and 3,000 psig, a space velocity between about 0.1 and 10 v/v/hr and a hydrogen rate between about 1,000 and 20,000 SCFB, a residue-containing petroleum oil feed containing at least 1 percent Conradson Carbon Residue and of which at least 10 percent by volume boils below about 1,000F. selected from the group consisting of whole crude, atmospheric residuum, vacuum residuum, shale oil, tar sand oil and residual fuel blends with a catalyst having a surface area of at least 300 m /g and a pore volume of at least 0.6 cclg comprising a member of the group consisting of iron, cobalt, nickel, their oxides and sulfides and a member of the group consisting of molybdenum, tungsten, their oxides and sulfides supported on a refractory inorganic oxide selected from the group consisting of alumina, zirconia, silica, magne-- sia and mixtures thereof and containing at least 2 percent by weight silica, separating the effluent into a light fraction boiling up to about 1,000F. and a heavy fraction having an initial boiling point of about 1,000F., contacting said light fraction in a second catalytic desulfurization zone with a desulfurization catalyst comprising a member of the group consisting of iron, cobalt, nickel, their oxides and sulfides and a member of the group consisting of molybdenum, tungsten, their oxides and sulfides on a refractory inorganic oxide selected from the group consisting of alumina, zirconia, silica, magnesia and mixtures thereof at a temperature between about 450 and 900F., a pressure between about 300 to 3,000 psig, a space velocity between about 0.1 and 20 and a hydrogen rate between about 500 and 20,000 SCFB and combining the desulfurized light fraction with said heavy fraction.

2. The process of claim 1 in which the catalyst in the first desulfurization zone comprises cobalt and molybdenum.

3. The process of claim 1 in which the catalyst in the first desulfurization zone comprises nickel and molybdenum. 

2. The process of claim 1 in which the catalyst in the first desulfurization zone comprises cobalt and molybdenum.
 3. The process of claim 1 in which the catalyst in the first desulfurization zone comprises nickel and molybdenum.
 4. The process of claim 1 in which the petroleum oil feed comprises atmospheric reduced crude.
 5. The process of claim 1 in which the petroleum oil feed comprises vacuum residuum.
 6. The process of claim 1 in which the catalyst in the first desulfurization zone contains 2-4 percent by weight silica and the balance of the support is alumina. 